Hi! Welcome to the boards. I am a strict vegetarian myself, though not vegan. But I hate eggs and milk and now don't eat cheese because it makes sick. But I do eat honey.
First off, have you gone to a specialist and been tested? There are lots of diseases, such as Celiac Sprue (wheat allergies) that have similar symptoms and these can be ruled out with a blood test. There are also other more serious diseases that you would want to rule out.
After that, if you don't want to use medicine (which has really made a difference in my life, but I understand why you want to avoid it) I would buy Heather's book and focus on following her diet carefully. You can totally do this as a vegetarian. I make recipes off the board all the time subbing in soy meat for normal meat.
If you have any other questions let me know... I'm happy to help. And I understand what you mean about feeling fat all the time. A friend of mine and I joked once about looking pregnant when we are having an attack, even though neither of us are big people either. It's a pain.